WiFi used to detect weapons and explosives

A new system based on ordinary WiFi can detect weapons, bombs and explosive chemicals in bags to improve security at public venues like museums, stadiums and theme parks.

According to a study led by Rutgers University in New Jersey, wireless internet signals in most public places can penetrate bags to get the dimensions of dangerous metal objects and identify them, including weapons, aluminium cans, laptops and batteries for bombs. WiFi can also be used to estimate the volume of liquids such as water, acid, alcohol and other chemicals for explosives, the researchers say.

This low-cost system requires a WiFi device with two to three antennas and can be integrated into existing WiFi networks. The system analyses what happens when wireless signals penetrate and bounce off objects and materials.

Experiments with 15 types of objects and six types of bags demonstrated detection accuracy rates of 99% for dangerous objects, 98% for metal and 95% for liquid. For typical backpacks, the accuracy rate exceeds 95% and drops to about 90% when objects inside bags are wrapped, said Yingying (Jennifer) Chen, study co-author and a professor in the Department of Electrical and Computer Engineering at Rutgers-New Brunswick’s School of Engineering.

“In large public areas, it’s hard to set up expensive screening infrastructure like what’s in airports,” Chen explained. “Manpower is always needed to check bags and we wanted to develop a complementary method to try to reduce manpower.”

Next, the researchers hope to boost the system’s accuracy in identifying objects by imaging their shapes and estimating liquid volumes.